Curcumin, which is a yellow pigment of ukon or turmeric (scientific name; Curcuma longa) which is a spice component of curry, is classified as curcuminoid, a kind of polyphenol. Therefore, curcumin is known as an antioxidant so that it is used not only as a natural pigment but also in health drinks and health foods having an improvement action of a lever function. Curcumin is also known to have an antitumor action, an antioxidant action, an anti-immune action, and the like; and thus, it is expected to be widely utilized in a medical drug. On the other hand, γ-oryzanol is a compound included in rice bran and so forth, and whereby it has many health effects such as reduction of blood lipids, growth facilitation, and easing of a menopause symptom, so that it is utilized in a medical drug, besides foods and cosmetics.
Both curcumin and γ-oryzanol are substances hardly soluble in water so that improvement in an absorption property thereof into a living body is required. In order to solve this problem, it is presumed that micronization of these substances to the size of less than several micrometers is effective (Patent Document 1).
With regard to the micronization method of curcumin, as described in Patent Document 2, a method is known in which after the turmeric pigment is added into a ghatti gum-including aqueous solution, the turmeric pigment is subjected to the crushing treatment until the average particle diameter thereof reaches 1 μm or less. However, the treatment time thereof is very long; and in addition, because a media mill such as a bead mill is generally used in the crushing treatment, there remains a problem of generating foreign materials derived from the media, so that the improvement thereof is required.
In the method in which curcumin is crushed by using a mechanical crusher such as a homogenizer, not only uniform micronization of curcumin is difficult but also there is a problem in durable stability. In order to solve these problems, in Patent Document 3, a method is described in which an ethanol solution having curcumin dissolved therein is mixed with and dispersed into a raw material water so as to micronize curcumin thereby obtaining a dispersion solution of finely crushed curcumin with the size of 200 nm or less. Specifically, in Example 3 of Patent Document 3, as the ethanol solution having curcumin dissolved therein, an ethanol solution having 0.5 g of 98% curcumin dissolved into 100 mL of 95% ethanol is prepared. In this Example 3, the temperature condition at the time of preparation of the ethanol solution is not described; however, because solubility of curcumin in ethanol is about 0.5% by weight (25° C.), curcumin is micronized by using the almost saturated ethanol solution thereof. However, because the curcumin concentration in the ethanol solution is too dilute, many problems are pointed out such as the waste water treatment and removal of ethanol in the subsequent processes, as well as the large processing facility. These backgrounds are also the same in γ-oryzanol (Patent Document 4). Accordingly, methods for efficiently producing microparticles with low industrial cost are required in both curcumin and γ-oryzanol.